Why not just make the thread prefix field "click through" to the appropriate Wiki index page?

All Wiki index pages have a navigation bar (including a return to forum link).

Then the "Master Index" sticky can go away all together.

Some web pages are (correctly) linked into multiple indexes, but can only have one prefix.

An app that only runs on a K4 or K5 would go into its "type of app" index, and into the K4 and K5 indexes. A developer would find it as an example in the "type of app" index that he wants to develop for. A K4 user would find it in the K4 index without needed to search each "type of app" index/

You cannot do that just with prefixes on a thread. But if you meant having a prefix field at the top of the forum, then that COULD do the job.

The way it is done now, the sticky thread can also have new non-prefixed indexes added to it, if we need to...